Thin-film magnetic head and method of forming the same

ABSTRACT

In a thin-film magnetic head having a multilayered film developing a magnetoresistive effect, which is present between an upper shielding layer and a lower shielding layer both formed above an AlTiC substrate, a recess for defining the lower shielding layer is formed in an underlayer present on a surface of the AlTiC substrate, and a lower shielding layer made of NiFe is provided in the recess. A SiO 2  film is interposed between the underlayer and the lower shielding layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thin-film magnetic head(magnetoresistive head) for reading (and writing) information withhigh-density recording by utilizing the magnetoresistive effect, and amethod of forming the thin-film magnetic head.

2. Description of the Related Art

A thin-film magnetic head for reproduction includes, in its basicstructure, a multilayered film developing the magnetoresistive effectbetween an upper shielding layer and a lower shielding layer, which areformed above an AlTiC substrate. A thin-film magnetic head is also knownwhich is constituted as a recording/reproducing head by forming, on thethin-film magnetic head for reproduction, a thin-film inductive head forrecording (magnetoresistive recording head). Roughly speaking, thethin-film magnetic head for recording and reproduction is constructed bysuccessively forming a lower shielding layer, a lower gap layer, amagnetoresistive sensor, an upper gap layer, an upper shielding layer,and a lower core layer (in the case of a piggyback type structure) (or,as an alternative, a merged type structure is obtained in which theupper shielding layer serves also as the lower core layer), and then bysuccessively forming, on the lower core layer, a magnetic pole sectionand a coil layer both positioned to locate in an Air Bearing Surface(ABS), a gap layer, an upper core layer, and a barrier layer.

In the process of manufacturing such a thin-film magnetic head forreproduction and a thin-film magnetic head for recording andreproduction, a magnetic film serving as the lower shielding layer hasbeen formed over an entire substrate surface in the past. However, it isa recent prevailing tendency to reduce an area in which the lowershielding layer is formed (i.e., to form a partial lower shieldinglayer) for the purpose of either reducing the probability of ashort-circuit with a wiring pattern ofa multilayered film or improvingthe reproduction performance.

Hitherto, such a partial lower shielding layer has been formed throughthe following steps. On an AlTiC substrate having a substrate protectivelayer made of alumina (Al₂O₃), a resist is formed by photolithography todefine an area in which the lower shielding layer is to be formed. Then,a soft magnetic material constituting the lower shielding layer, such asPermalloy (NiFe), is plated (by frame plating) over the entire substratesurface under a magnetic field. After removing useless layers includingthe resist, an alumina film is formed over the entire substrate surfaceincluding the lower shielding layer. Then, the alumina is scrapped offby a Chemical Mechanical Polishing(CMP) step until the lower shieldinglayer is exposed.

The above-described conventional method of forming the partial lowershielding layer, however, essentially requires expensive equipment andan additional step for forming analumina film. Also, a strong-acidslurry is usually employed in the polishing CMP step of scraping off thealumina film until the lower shielding layer is exposed. However,because polishing rates of alumina and a soft magnetic material, such asPermalloy, are substantially equal to each other, it is typicallydifficult to control the film thickness of the lower shielding layer(i.e., deciding when to end the CMP step). Further, the alumina surfaceis typically corroded and roughed with the use of a strong-acid slurry.In addition, in a photolithography step of forming a resist layer todefine a track width of a magnetoresistive sensor, a film thicknessdistribution of the resist layer is not uniform and a variation mayoccur in the track width of the magnetoresistive sensor.

SUMMARY OF THE INVENTION

Taking into account the above-mentioned problems with the conventionalprocess of forming a partial lower shielding layer, it is an object ofthe present invention to provide a thin-film magnetic head and a methodof forming the thin-film magnetic head, which can easily control a filmthickness of the lower shielding layer with no need foradditionalformation onan alumina film. Also, it is an object of the presentinvention to provide a thin-film magnetic head and a method of formingthe thin-film magnetic head, which can define a track width of amagnetoresistive sensor with high accuracy, the sensor being formedafter forming the lower shielding layer, and which is adaptable for atendency toward a narrower track.

An AlTiC substrate generally requires, as a substrate protective layer,an underlayer made of alumina. The underlayer prevents an electricalshort-circuit possibly occurring between the conductive AlTiC substrateand external devices. In view of the presence of such an underlayer, thepresent invention has been accomplished based on the finding thatequipment for forming an alumina film and an additional step of formingthe alumina film are no longer required by utilizing the underlayer todefine an area, in which the partial lower shielding layer is to beformed. More specifically, the present invention provides a thin-filmmagnetic head wherein a multilayered film developing a magnetoresistiveeffect is present between an upper shielding layer and a lower shieldinglayer both formed above an AlTiC substrate, a recess for defining thelower shielding layer is formed in an underlayer present on a surface ofthe AlTiC substrate, and a lower shielding layer made of a soft magneticmaterial is provided in the recess.

In the present invention, to facilitate the control of a film thicknessof the lower shielding layer, a SiO₂ film can be interposed between theunderlayer and the lower shielding layer. By employing the SiO₂ film asa stopper in the CMP step of polishing the lower shielding layer, theduration of the polishing step can be easily determined because the SiO₂film has a lower polishing rate than alumina. Also, because the SiO₂film has a higher dielectric voltage withstand than alumina, thepresence of the SiO₂ film provides another advantage in that theinsulation (voltage withstand) between the lower shielding layer and theAlTiC substrate can be improved. Further, because the SiO₂ film has ahigher corrosion resistance to a strong-acid slurry than alumina, thepolished surface can be kept flat. Accordingly after the polishing step,in a step of forming a resist layer to define a track width of amagnetoresistive sensor, a film thickness distribution of the resistlayer can be made uniform and the track width of the magnetoresistivesensor can be defined with high accuracy. Consequently, a thin-filmmagnetic head can be obtained which is suitable for a higher recordingdensity engendered from a tendency toward narrower tracks.

According to another aspect, the present invention provides a method offorming a thin-film magnetic head, the method comprising the steps ofpreparing an AlTiC substrate having an underlayer and forming, in theunderlayer, a lower-shielding formed recess corresponding to an area inwhich a lower shielding layer is to be formed; forming a SiO₂ film on asubstrate surface including the lower-shielding formed recess; forming alower shielding layer made of a soft magnetic material on the SiO₂ film;and polishing the lower shielding layer with the SiO₂ film serving as astopper until the SiO₂ film is exposed. With this forming method, theSiO₂ film is formed to interpose between the underlayer and the lowershielding layer. After the step of polishing the lower shielding layer,a step of removing the SiO₂ film other than the SiO₂ film in thelower-shielding formed recess may be performed so that an upper surfaceof the lower shielding layer and an upper surface of the underlayerdefine the same plane (flat plane).

According to still another aspect, the present invention provides amethod of forming a thin-film magnetic head, the method comprising thesteps of preparing an AlTiC substrate having an underlayer and forming aSiO₂ film on the underlayer; forming, through the SiO₂ film and partlyin the underlayer, a lower-shielding formed recess corresponding to anare-a in which a lower shielding layer is to be formed; forming a lowershielding layer made of a soft magnetic material on a substrate surfaceincluding the lower-shielding formed recess; and polishing the lowershielding layer with the SiO₂ film serving as a stopper until the SiO₂film is exposed. With this forming method, since the SiO₂ film presentin the area in which the lower shielding layer is to be formed isremoved, the lower shielding layer is directly formed on the underlayerin the lower-shielding formed recess. After the step of polishing thelower shielding layer, a step of removing the SiO₂ film may be performedso that the upper surface of the lower shielding layer and the uppersurface of the underlayer constitutes the same plane.

The lower-shielding formed recess is preferably formed by ion milling,or the like, so that the shape and the depth of the lower-shieldingformed recess can be appropriately controlled.

In the above-described thin-film magnetic head and method of forming thethin-film magnetic head, the underlayer present on the AlTiC substrateis generally formed of alumina. Also, NiFe can be employed as the softmagnetic material forming the lower shielding layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view, as viewed from the side of a head surface(ABS surface) positioned to face a recording medium, showing an overallmultilayered structure of a thin-film magnetic head according to a firstembodiment of the present invention;

FIG. 2 is an enlarged partial sectional view of a multilayered structurearound a lower shielding layer of the thin-film magnetic head shown inFIG. 1;

FIG. 3 is a sectional view showing one step of a method of forming thelower shielding layer shown in FIGS. 1 and 2;

FIG. 4 is a sectional view showing a step carried out subsequent to thestep shown in FIG. 3;

FIG. 5 is a sectional view showing a step carried out subsequent to thestep shown in FIG. 4;

FIG. 6 is a sectional view showing a step carried out subsequent to thestep shown in FIG. 5;

FIG. 7 is an enlarged partial sectional view of a multilayered structurearound a lower shielding layer of a thin-film magnetic head according toa second embodiment of the present invention;

FIG. 8 is a sectional view showing one step of a method of forming thelower shielding layer shown in FIG. 7;

FIG. 9 is a sectional view showing a step carried out subsequent to thestep shown in FIG. 8;

FIG. 10 is a sectional view showing a step carried out subsequent to thestep shown in FIG. 9; and

FIG. 11 is a sectional view showing a step carried out subsequent to thestep shown in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a sectional view, as viewed from the side of a head surface(ABS surface) positioned to face a recording medium, showing an overallmultilayered structure of a thin-film magnetic head 1 according to afirst embodiment of the present invention. The thin-film magnetic head 1is a thin-film magnetic head for reproduction, which is provided at atrailing-side end of a floating slider of a hard disk drive, forexample. In FIG. 1, X-, Y- and Z-directions are defined respectively asa direction of a track width, a direction of a magnetic field leakedfrom the recording medium, and a moving direction of the recordingmedium.

The thin-film magnetic head 1 has a substrate (AlTiC substrate) 11 madeof aluminum-titanium-carbide (AlTiC). On a surface of the AlTiCsubstrate 11, an underlayer 12 made of alumina is formed as a substrateprotective layer in advance.

On the AlTiC substrate 11, a lower shielding layer 13, a lower gap layer14, a magnetoresistive sensor 2, an upper gap layer 17, and an uppershielding layer 18 are successively formed in this order from thesubstrate side. The lower shielding layer 13 and the upper shieldinglayer 18 are each formed of a soft magnetic material. The lower gaplayer 14 and the upper gap layer 17 are each formed of a nonmagneticmaterial. The magnetoresistive sensor 2 is constituted as a multilayeredfilm formed as a substantially trapezoidal section and developing themagnetoresistive effect. The magnetoresistive sensor 2 can be practicedas any Giant Magnetoresistive (GMR) sensors, an AnisotropicMagnetoresistive (AMR) sensor and so on.

On each of-both sides of the magnetoresistive sensor 2 in the directionof the track width, a bias layer 15 made of a highly magnetic material,such as a CoPt alloy, and an electrode layer 16 made of an electricallyconductive material, such as Au, are successively formed in this orderfrom the side of the lower gap layer 14. The upper gap layer 17 and theupper shielding layer 18 are positioned on the electrode layers 16.Though not shown, a bias buffer layer made of a metal film, such as Cror Ta, is formed between the lower gap layer 14 and the bias layer 15.

In the thin-film magnetic head 1 having the overall structure describedabove, as shown in FIG. 2, the lower shielding layer 13 is provided in astate embedded in the underlayer 12. More specifically, the underlayer12 has a recess 12 a formed therein to define the lower shielding layer13, and the lower shielding layer 13 is provided in the recess 12 a.FIG. 2 is an enlarged partial sectional view of a multilayered structurearound the lower shielding layer 13. The recess 12 a is formed by ionmilling in a position corresponding to a lower-shielding formed area,and it restricts the shape and the film thickness of the lower shieldinglayer 13 to be formed.

Defining the lower-shielding formed area (recess 12 a) with utilizationof the underlayer 12, as described above, provides a structure in whichthe underlayer 12 is present around the lower shielding layer 13 formedin the lower shielding formed area, and an upper surface 12 b of theunderlayer 12 and an upper surface 13 a of the lower shielding layer 13can constitute the same plane (flat plane). A step of additionallyforming an alumina layer to make flat the surroundings of the lowershielding layer 13 is no longer required, and additional equipment forforming an alumina film is also no longer required. Accordingly, theequipment investment can be greatly cut down.

The lower shielding layer 13 is a layer formed, in accordance with theshape and the depth (length in the Z-direction) of the recess 12 a, inan area substantially equal to the upper shielding layer 18 within arange not impairing the shielding function in the direction of the trackwidth. More specifically, the lower shielding layer 13 can be formedsuch that its length in the direction of the track width is set largerthan the length of the magnetoresistive sensor 2 in the same directionand substantially equal to the length of the upper shielding layer 18 inthe same direction.

The lower shielding layer 13 also has the function of radiating heatgenerated from the magnetoresistive sensor 2. By forming, in theunderlayer 12, the recess 12 a for defining the lower shielding layer 13like this embodiment, the film thickness of the underlayer 12 positionedjust under the lower shielding layer 13 is reduced, and thereforethermal conductivity from the lower shielding layer 13 to the AlTiCsubstrate 11 is improved. Hence, even with the lower shielding layer 13formed as a partial lower shielding layer, the heat generated from themagnetoresistive sensor 2 can be effectively radiated from the AlTiCsubstrate 11 through the lower shielding layer 13.

A method of forming the lower shielding layer 13 of the thin-filmmagnetic head 1, shown in FIGS. 1 and 2, will be described below withreference to FIGS. 3 to 6. Note that FIGS. 3 to 6 are partial sectionalviews, as viewed from the side of the head surface positioned to facethe recording medium.

First, as shown in FIG. 3, a SiO₂ film 19 is formed over an entiresurface of the underlayer 12 present on the AlTiC substrate 11. The SiO₂film 19 functions as a polishing stopper in a polishing step describedlater. The SiO₂ film 19 can be formed by sputtering or IBD (Ion BeamDeposition). The underlayer 12 present on the AlTiC substrate 11 used inthis embodiment has a film thickness of about 2.0 μm, and the SiO₂ film19 has a film thickness of about 0.4 μm, for example.

After forming the SiO₂ film 19, the lower-shielding formed area ispatterned on an upper surface of the SiO₂ film 19 by photolithography.In a position corresponding to the patterned lower-shielding formedarea, the recess 12 a is formed through the SiO₂ film 19 and partly inthe underlayer 12 (FIG. 4). Because the recess 12 a restricts the shapeand the film thickness of the lower shielding layer 13 to be formed, therecess 12 a is preferably formed with high precision by ion milling. Inthis embodiment, the recess 12 a restricts the length of the lowershielding layer in the direction of the track width to be larger thanthe length of the magnetoresistive sensor 2 in the same direction, whichis formed above the lower shielding layer, and to be equal to the lengthof the upper shielding layer 18 in the same direction. The recess 12 ahas a depth of about 1.4 μm, for example.

Subsequently, as shown in FIG. 5, a NiFe layer 13′ serving as the lowershielding layer is formed on the entire surface (over the SiO₂ film 19and the recess 12 a) by plating. The NiFe layer 13′ has a film thicknessof about 2.0 μm.

Then, the NiFe layer 13′ is polished by CMP (Chemical MechanicalPolishing) until the SiO₂ film 19 is exposed, whereby the lowershielding layer 13 is formed as shown in FIG. 6. In this step, the SiO₂film 19 functions as a stopper for the polishing. The SiO₂ film 19 hasproperties that it is highly endurable against an acid and alkali andhas a polishing rate lower than that of the NiFe layer 13′. In the CMPstep of this embodiment, a polishing rate ratio of the SiO₂ film 19 tothe NiFe layer 13′ is about 1:25. Because of such a difference inpolishing rate, even when the polishing step with the CMP is continuedafter the SiO₂ film 19 has been exposed, the lower shielding layer 13 ishardly polished and the film thickness of the lower shielding layer 13is kept at the same value as that immediately after the SiO₂ film 19 hasbeen exposed. In other words, even if the timing of bringing the CMPinto an end is shifted to some extent, the film thickness of the formedlower shielding layer 13 is not affected. Thus, by employing the SiO₂film 19 as a stopper for the polishing, it is possible to properly andeasily control the film thickness of the lower shielding layer 13.

After the end of the polishing step with the CMP, the SiO₂ film 19 onthe underlayer 12 may be removed by RIE (Reactive Ion Etching) usingCF₄, for example. Through the above-described steps, the lower shieldinglayer 13 shown in FIG. 2 is obtained. At this time, since the uppersurface 13 a of the lower shielding layer 13 and the upper surface 12 bof the underlayer 12 constitute a flat plane, a step of forming analumina layer to make flat the surroundings of the lower shielding layer13 is no longer required. In the illustrated embodiment, the lowershielding layer 13 has a film thickness of about 1.0 to 1.3 μm.

After forming the lower shielding layer 13, other layers constitutingthe thin-film magnetic head, such as the lower gap layer and themagnetoresistive sensor, are successively formed on the lower shieldinglayer 13 in the predetermined order according to the usual manner,whereby the thin-film magnetic head 1 shown in FIG. 1 is obtained.Incidentally, removing the SiO₂ film 19 on the underlayer 12 is notessential and the subsequent steps may be continued without removing theSiO₂ film 19.

FIG. 7 is an enlarged partial sectional view, as viewed from the side ofa head surface positioned to face a recording medium, of a multilayeredstructure around a lower shielding layer of a thin-film magnetic headaccording to a second embodiment of the present invention. This secondembodiment differs from the first embodiment in that, to increaseinsulation between the lower shielding layer 13 and the AlTiC substrate11, a SiO₂ film 19 having a higher dielectric voltage withstand thanalumina constituting the underlayer 12 is interposed between theunderlayer 12 and the lower shielding layer 13. In FIG. 7, constituentelements having the same functions as those in the first embodiment aredenoted by the same reference symbols as those in FIGS. 1 and 2. As withthe first embodiment, though not shown in FIG. 7, other layersconstituting the thin-film magnetic head, such as a lower gap layer anda magnetoresistive sensor, are successively formed on the lowershielding layer 13 in the predetermined order.

FIGS. 8 to 11 are partial sectional views, as viewed from the side ofthe head surface positioned to face the recording medium, showingsuccessive steps of a method of forming the lower shielding layer 13shown in FIG. 7. This illustrated embodiment employs an AlTiC substrate11 having an underlayer 12 with a film thickness of about 2.0 μm, forexample.

First, a lower-shielding formed area is patterned on an upper surface ofthe underlayer 12 on the AlTiC substrate 11 by photolithography. At aposition corresponding to the patterned lower-shielding formed area, arecess 12 a having a depth of about 1.0 μm, for example, is formed inthe underlayer 12 (FIG. 8). The recess 12 a is preferably formed by ionmilling. The recess 12 a can be formed, for example, so as to restrictthe length of the lower shielding layer in the direction of the trackwidth to be larger than the length of the magnetoresistive sensor 2 inthe same direction, which is formed above the lower shielding layer, andto be substantially equal to the length of the upper shielding layer 18in the same direction.

Then, a SiO₂ film 19 is formed over an entire surface of the underlayer12 including the recess 12 a (FIG. 9). The SiO₂ film 19 is formed inthickness of 0.4 μm, for example, by sputtering or IBD. Subsequently, asshown in FIG. 10, a NiFe layer 13′ serving as the lower shielding layeris formed on an entire surface of the SiO₂ film 19 by plating. The NiFelayer 13′ has a film thickness of about 2.0 μm.

Then, the NiFe layer 13′ is polished by CMP (Chemical MechanicalPolishing) until the SiO₂ film 19 positioned around the recess 12 a isexposed, whereby the lower shielding layer 13 is formed as shown in FIG.11. In this CMP step, the SiO₂ film 19 positioned around the recess 12 afunctions as a stopper for the polishing. More specifically, because ofa difference in polishing rate between the SiO₂ film 19 and the NiFelayer 13′, even when the polishing step with the CMP is continued afterthe SiO₂ film 19 has been exposed, the NiFe layer 13′ is hardlypolished. Thus, it is possible to properly and easily control the filmthickness of the lower shielding layer 13.

After the end of the polishing step with the CMP, the SiO₂ film 19positioned around the recess 12 a may be removed by Reactive IonEtching, (RIE), using CF₄. Through the above-described steps, the lowershielding layer 13 shown in FIG. 7 is obtained. At this time, since anupper surface 13 a of the lower shielding layer 13 and an upper surface12 b of the underlayer 12 constitute a flat plane, a step of forming analumina layer to make flat the surroundings of the lower shielding layer13 is no longer required. Assuming, as described above, that the depthof the recess 12 a is about 1.0 μm and the film thickness of the SiO₂film 19 is about 0.4 μm, the total thickness of the lower shieldinglayer 13 and the SiO₂ film 19 is about 1.1 to 1.3 μm.

Although the SiO₂ film 19 positioned around the recess 12 a is removedas described above, the SiO₂ film 19 still remains in the recess 12 abetween the lower shielding layer 13 and the underlayer 12 even afterthe end of the polishing step with the CMP. The presence of the SiO₂film 19 between them increases insulation between the lower shieldinglayer 13 and the AlTiC substrate 11, and hence makes it possible toeffectively prevent electrostatic breakdown even with the lowershielding layer 13 formed as a partial lower shielding layer.

After forming the lower shielding layer 13, other layers constitutingthe thin-film magnetic head, such as the lower gap layer and themagnetoresistive sensor, are successively formed on the lower shieldinglayer 13 in the predetermined order according to the usual manner,whereby the thin-film magnetic head similar to that shown in FIG. 1 isobtained. Incidentally, removing the SiO₂ film 19 positioned around therecess 12 a is not essential and the subsequent steps may be continuedwithout removing the SiO₂ film 19.

While the thin-film magnetic head 1 according to each of theabove-described embodiments is a thin-film magnetic head forreproduction, a thin-film magnetic head for recording and reproductionis generally constructed by forming a thin-film inductive head forrecording (magnetoresistive recording head) above the thin-film magnetichead 1 (in the Z-direction). Roughly speaking, a thin-film magnetic headfor recording and reproduction is constructed by successively formingthe lower shielding layer 13, the lower gap layer 14, themagnetoresistive sensor 2, the upper gap layer 17 and the uppershielding layer 18, then forming a lower core layer on the uppershielding layer 18 (in the case of a piggyback type structure) (or, asan alternative, a merged type structure is obtained in which the uppershielding layer serves also as the lower core layer), and then bysuccessively forming, on the lower core layer, a magnetic pole sectionand a coil layer both positioned to locate in an ABS (Air BearingSurface), an upper core layer, and a barrier layer. The presentinvention is also of course applicable to such a thin-film magnetic headfor recording and reproduction.

To prevent any thin-film head expansion or distortion, a substantialamount of heat generated by the coil layer of the recording head needsto be dissipated. Thin-film magnetic head expansion or distortion due toheat tend to cause the thin-film magnetic head to project out of the ABSsurface and then damage (or erase) the recording medium (or magneticinformation recorded on the recording medium). Whereas, within thecurrent embodiments, since the film thickness of the underlayerpositioned just under the lower shielding layer is reduced, the thermalconductivity from the lower shielding layer to the AlTiC substrate isthereforeimproved and the heat generated from the magnetoresistivesensor and the coil layer can be effectively dissipated from the AlTiCsubstrate through the lower shielding layer. As a result, potentialtroubles caused by the heat generated from the magnetoresistive sensorand the coil layer can be effectively prevented.

According to the present invention, the recess for defining the lowershielding layer is formed in the underlayer present on the AlTiCsubstrate, and the lower shielding layer is formed in the recess. Hence,a step of forming an alumina layer to make flat the upper surface of thelower shielding layer including the surroundings thereof is no longerrequired, and the equipment investment can be greatly cut down. Further,since the underlayer has a reduced film thickness in its areacorresponding to the recess, the heat generated from themagnetoresistive sensor and the coil layer can be effectively dissipatedand potential troubles caused by the generated heat can be effectivelyprevented.

Also, according to the present invention, the SiO₂ film is employed as astopper in the step of polishing the lower shielding layer. Because of adifference in the polishing rates between the SiO₂ film and the softmagnetic material constituting the lower shielding layer, the filmthickness of the lower shielding layer can be precisely and easilycontrolled. In addition, according to the present invention, since theSiO₂ film is present between the underlayer and the lower shieldinglayer, insulation between the AlTiC substrate and the lower shieldinglayer can be improved.

1-5. (Cancelled)
 6. A method of forming a thin-film magnetic head, themethod comprising the steps of: preparing an AlTiC substrate having anunderlayer and forming, in said underlayer, a lower-shielding formedrecess corresponding to an area in which a lower shielding layer is tobe formed; forming a SiO₂ film on a substrate surface including saidlower-shielding formed recess; forming a lower shielding layer made of asoft magnetic material on said SiO₂ film; and polishing said lowershielding layer with said SiO₂ film serving as a stopper until said SiO₂film is exposed.
 7. (Cancelled)
 8. A method of forming a thin-filmmagnetic head according to claim 6, wherein said underlayer is made ofalumina.
 9. (Cancelled)
 10. A method of forming a thin-film magnetichead according to claim 6, wherein said lower-shielding formed recess isformed by ion milling.
 11. A method of forming a thin-film magnetic headaccording to claim 6, further comprising a step of removing said SiO₂film other than the SiO₂ film in said lower-shielding formed recessafter the step of polishing said lower shielding layer.
 12. (Cancelled)13. A method of forming a thin-film magnetic head according to claim 6,wherein said lower shielding layer is made of NiFe.